There are known in the patent literature various techniques for carrying out borehole measurements employing NMR. Particularly useful techniques and apparatus for carrying out such techniques are described in U.S. Pat. Nos. 4,710,713 and 4,717,878 of the present assignee. U.S. Pat. No. 4,933,638 describes a technique which is based thereon.
It is known to carry out laboratory tests of the self-diffusion coefficient, i.e. the rate at which molecules of a material randomly travel within the bulk of the same material, on cores. Providing the cores for testing is a very expensive and time consuming process and is not suitable for sampling a large extent of a borehole.
A representative listing of relevant publications in this field is set forth hereinbelow:
J.H. Simpson and H.Y. Carr, Diffusion and Nuclear Spin Relaxation in Water, The Physical Review, 111, No. 5, Sep. 1, 1958, p 1201 ff.
D.C. Douglass and D.W. McCall, Diffusion in Paraffin Hydrocarbons, Journal of Physical Chemistry, 62, 1102 (1958);
D.E. Woessner, N.M.R. Spin Echo Self Diffusion Measurements on Fluids Undergoing Restricted Diffusion, Journal of Physical Chemistry, 87, 1306 (1963);
R.C. Wayne and R.M. Cotts, Nuclear Magnetic Resonance Study of Self-Diffusion in a Bounded Medium, Physical Review, 151, No. 1, Nov. 4, 1964;
E.O. Stejskql and J.E. Tanner, Spin Diffusion Measurements: Spin Echoes in the Presence of a Time Dependent Field Gradient, The Journal of Chemical Physics, Vol. 42, No. 1, 288-292, Jan. 1, 1965.
K.J. Packer and C. Rees, Pulsed NMR Studies of Restricted Diffusion, Journal of Colloid and Interface Science, Vol. 40, No. Aug. 2, 1972;
C.H. Neuman, Spin echo of spins diffusing in a bounded medium, The Journal of Chemical Physics, Vol. 60, No. 11, Jun. 1, 1974;
W.D. Williams, E.F.W. Seymour and R. M. Cotts, A Pulsed Gradient Multiple-Spin Echo NMR Technique for Measuring Diffusion in the Presence of Background Magnetic Field Gradients, Journal of Magnetic Resonance 31, 271-282, (1978);
U.S. Pat. No. 4,719,423 describes NMR imaging of materials for transport properties including diffusion coefficients. This patent relates to imaging of core samples and not in situ;
P.T. Callaghan, D. Macgowan, K.J. Packer and F.O. Zelaya, High Resolution q-space Imaging in Porous Structure, submitted for publication in the Journal of Magnetic Resonance, 1990;
U.S. Pat. No. 4,350,955 of J.A. Jackson et al. and other publications of J.A. Jackson on the same general subject.